Project Summary/Abstract: Lung and breast cancer are two of the most common cancers in the United States with an estimated 224,390 and 246,660 new cases in 2016, respectively. Current treatment regimens for these cancers include extensive chemotherapy, surgery, and radiation therapy, but despite multiple modalities of treatment, the 5 year survival for lung cancer is only 17.7%, and the estimated number of deaths from breast cancer in 2016 is 40,450 individuals. Given these outcomes, new treatment options that can selectively kill cancer cells as well as early progenitor cancer stem cells that are believed to be responsible for development of drug resistance and metastasis are urgently needed. The repurposing of currently available relatively non-toxic FDA approved drugs such as D-penicillamine (DPEN) and disulfiram (DSF), which are possibly able to target fundamental differences in oxidative metabolism in cancer versus normal cells, could provide a promising and rapidly translatable strategy to target these deadly cancers. Preliminary data generated by the applicant has shown for the first time that DPEN and DSF are selectively toxic to breast and lung cancer cells, relative to normal breast and lung epithelial cells, when combined with physiologically relevant non-toxic concentrations of copper, and this toxicity was dependent on H2O2-mediated oxidative stress. In addition, DPEN and DSF were found to be capable of enhancing the effects of radiation on lung cancer cells and were able to inhibit the increased percentage of viable cancer stem cells (as detected by ALDH1 activity) in bulk populations of lung cancer cells exposed to radiation. These promising preliminary results have led to the overarching hypothesis that: DPEN and DSF selectively induce cytotoxicity and radio-chemo-sensitization in human breast and lung cancer cells (versus normal cells) and cancer stem cells via H2O2-mediated oxidative stress that is mitigated by disruptions in intracellular redox active metal ions. Aim 1 of this proposal will determine in vitro if DPEN and DSF are differentially cytotoxic to lung and breast cancer cells (versus normal cells) via H2O2-mediated oxidative stress and disruptions in redox active metal ions. Aim 2 will determine if DPEN and DSF combined with ionizing radiation and/or standard chemotherapy will selectively (relative to normal cells) enhance cancer cell cytotoxicity in vitro and in vivo via a mechanism mediated by H2O2, redox active metal ions, and suppression of cancer stem cell survival. The successful completion of these studies will define biochemical mechanisms underlying DPEN and DSF selective toxicity in cancer versus normal cells and will provide new means for exploiting fundamental differences in oxidative metabolism between these cell populations in order to increase treatment efficacy using traditional cancer therapies. The proposed project will also allow the applicant to expand her basic science investigational skills, experimental knowledge base, and detailed mechanistic understanding of redox biology as it relates to cancer therapy that will greatly facilitate her ultimate goal of becoming a successful physician scientist faculty member and PI in translational oncology.